CHAPTER ONE

INTRODUCTION

1.1 ORIGIN AND NATURE OF ACTIVATED CARBON

Carbon is the fifteenth most abundant element in the earth’s crust and the fourth

most abundant element in the universe by mass after hydrogen helium and

oxygen. Scientists industries and consumers use different forms of carbon and

carbon containing compounds in many ways such as activated carbon or carbon in

its active form which can be used to purify water among others.

Activated carbon is a form of carbon that has been produced to make it extremely

porous and thus have a very large surface area available for adsorption or chemical

reactions.

It can be defined as a microcrystalline non-graphitic amorphous form of carbon

which has been processed to develop a high internal porosity due to its network of

inter-connecting pores.

The history of activated carbon is dated since the fifteenth century during the

time of Columbus when sailors used to blacken the inside of wooden water barrels

with fire since they observed that the water would stay fresh much longer. It is

likely that people at that time proceeded by intuition only without having any

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insight into the mechanism of the effect. The mechanism was recognized

beginning from the eighteenth century.

In 1862 Lipscombe prepared a carbon material for purifying portable water. This

development paved the way for the commercial application of activated carbon

first for portable water and then in waste water sector.

1.2 METHODS OF MANUFACTURE OF ACTIVATED CARBON

The methods employed in the industrial manufacture of activated carbons are

numerous but consist of three main methods namely; Chemical activation Steam

activation and thermal processing techniques.

The raw materials or precursors used in the manufacture of activated carbon are as

follows; Softwood coconut shell lignite hardwood grain and agro products

bituminous coal anthracite etc.

Chemical activation is generally used for the production of activated carbon from

sawdust wood or peat and uses chemicals for activation. Chemical activation

technique involves mixing an inorganic chemical compound with the carbonaceous

raw materials and the most widely used activating agents are Phosphoric acid and

Zinc Chloride.

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Steam activation technique is generally used for coal-based coconut shell and

grain-based activated carbons and uses gases vapors or a mixture of both for its

activation.

Thermal processing technique is a separation process that removes unwanted

materials from the carbonaceous precursor used under varying heat applications.

This technique is at a lower cost compared to the two techniques above and meets

all environmental standards while others need expensive solutions to achieve the

same results.

1.3 NEED FOR PRESENT INVESTIGATION

The need for present investigation of this material cannot be over emphasized. This

is as a result of the pressing need for treatment of waste water emanating from

domestic and industrial concerns.

Activated carbon plays an important role in the purification of fluids (water)

including vegetable oils used in domestic cooking and as a precursor in industrial

manufacture of food products. The slow pace of technological development in the

country has resulted to the expenditure of the nation’s resources on importation of

activated carbons to meet the demand for local chemical and process industries as

well as the demand for municipal and industrial water treatment plants.

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Rapid industrialization together with the increase in modern methods of

agriculture and the increase in population has contributed to the pollution of the

ecosystem. Most of the pollutants are toxic to living organisms. It is therefore

imperative that waste water has to be treated to remove the toxic materials before

disposal to the environment. Most methods of treating water have some inherent

shortfalls. Activated carbon treatment was therefore developed because of its

effectiveness in pollutants removal especially in water purification.

1.4 OBJECTIVES AND SCOPE OF THE STUDY

The primary objectives and scope of the present investigation include the

following:

i. Acquisition of the different types of activated carbons available to the nation’s

chemical industry.

ii. Modification of the surface physical and chemical properties of the carbon

material for their use in liquid phase applications.

iii. Determination of the physical properties of the as-received and modified

activated carbon materials.

iv. Testing the adsorption capacity of the carbon materials in adsorption processes.

v. Evaluation of the fractional surface coverage for each carbon material.

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vi. Proposal of a scheme for the optimal modification of activated carbon material

for optimal application in liquid phase adsorption.

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